Office



I we M64161) I J H ROBERTSON.

' I ELEGTRICI TELEPHONE.

film-276,630. PatentedMay 1,1;1883. I my; w Is- 72.

I \(l I I i I I WT WITNESSES: I IJBTVBNTOR" ATTORNEY 1 JAMES ll. ROBERTSON,

PATENT Oriana OF NEYV YORK, N. Y.

ELECTRIC TELEPHONE.

SPECIFICATIONforming part of Letters Patent No. 276,630, dated May 1, 1883.

Application filed August 16, 1882- (No model.)

To all whom, it may concern..-

Be it known that 1, JAMES II. ROBERTSON, of the city of New York, in the county and State of New York, have invcnteda new and useful Improvement in Electric Telephones, of which the following is a specification, reference being had to the accon'ipanying drawin gs, forming part of the same.

My-invention relates to that class of electrictelephone transmitters in which the electric current passes through electrodes that are loosely in contact; and it consists in the devices hereinafter described and claimed, whereby magnetism is employed, instead of a spring or gravity, to produce contact-pressure of the electrodes, and whereby the magnetic force so employed maybe adj usted at pleasure.

Figure .of the drawings is a face view of thcmcch ni mof an ordinary telephone-transmitter with my-i111pl'o\-'c111ent added. Fig. 2 is an edge iew of the same, and Fig. 3 is a do 1aolicd'view of one of the electrodes and a portion of the magnet.

A is the diaphragm. It is shown attached to the door 13 of a case, which, when closed, .i'ncloscs the mechanism. The mouth-piece (not shown) is on the outer or opposite side of the door. The diaphragm is attached to the door at its perimeter, so as to leave it free to vibrate.

C is the fixed electrode, made preferably of carbon, attached rigidly to the center of the diaphragm.-

I) is the free electrode, also of carbon. It is suspended from the bracket E on the points a a by the wires ff, as shown, so as to be free to vibrate. It is preferably so arranged that by its own "'ravit it will han in contact with the iixcd electrode C, as shown in Fig. 2.

.h and F are the circuit-wires, one, 'lflbci ng connected to the diaphragm A, through which the current from the wire, i is conducted to the electrode 0. The other wire, 1*", is connected to the bracket I), thus establishing a ci rcuit-connection with the electrode 1) through the wires ff and pivotal points a a;

It is well known that in this class of instruments a yielding pressure must-be exerted up on the free electrode to maintain its contact with the lixod electrode on thediaphragm, and

that this pressure has to be made adjustable employed in using the telephone. Thispressure has usually been supplied by a springer by gravity; but in the use-of these agents for the purpose it is difficult to secure that fine-' ness and delicacy of action and adjustment necessary to produce the best results. I have found that magnetism is a much better agent for the purpose. In order to use the magnetic force conveniently and efliciently, I arrange a. fixed magnet with its poles in such relation to the free electrode D, which is attached to y a piece of iron or other metal susceptible to magnetic attract ion,that it (the said electrode) will be drawn and pressed by the magnet into contact with the electrode 0. Upon the-magnet I place a movable keeper, I, whichby being shifted to or from the poles of the magne will modify their magnetic force) Q In the drawings, G is the magnet, which is fixed in its position by being rigidly attached to the door B.

ilis the piece of iron to which the electrode D is attached. It projects laterally beyond the said electrode, as shown in the drawings, and acts as an armature to the magnet G. The extremities of the poles b b of the magnet are placed between the lower edge of the said ar-. mature II and the diaphragm A, as shown plainly in Fig. 2. The attraction exerted be tween the poles b b of the magnet and the armature II will, as is evident, draw the elec- 'trode D into contact with the electrode 0 with a pressure due to the force of the magnet.

I is a keeper consisting of a flat bar of iron or steel placed upon'thc magnet, where it will be held by magnetic attraction. According as this keeper is placed nearer to or farther from the poles of the magnet is the magnetic force at the poles loss or greater. By these means the contact-pressure of the electrode D upon the electrode ()is increased or diminsaid armature and thc'wires f f by which it is suspended from the bracket E, downward,

thus insuring continuous and perfect metallic contact at the points a a. 5 The specialdevices above described for suspending; and pivoting the tree electrode, while I regard them as'new I do not intend to claim them in this specification, but reserve them for a separate patent, for which it is my purpose 1o,.;.t o ,apply..., Nor do Iintend'to limit myself here to the said special devices-i1amely, the bracket E, the wires f f the points a a, and

' to the diaphragm, the said rod being, pivoted,

intermediate itsends on auaxlc, so that the magnet, acting to attract the armature end of said rod away from the fixed electrode, there- .by swings the opposite, end toward the diaphragm,into contact with the fixed electrode, and the adjustment is accomplished by moving the magnebnearer to or farther away from the said arngatnre; but this method ofemploying the magnetic l'orce is objectionable, both" because of the inertia of the comparatively large mass of carbon and metal of which the 3 5 swingingcarbon rod and arlnatnreinnst necessarily consist, and because of the jarring and I lost motion that are liable to occur at the axial joint. The devices which I haveldescribed and to which 1 limit my claims obviate these objections.

\Vhat I claim as my invention, and desire to secure by Letters Patent, is a 1. The combination, in an electric-telephone transmitter, of the diaphragm A, the electrode C, fixed to the diaphragm, the swinging elec-' trodc D, to which is attached the armature H, and a magnet G, the poles of which are between the said diaphragm and armatnrc,bnt hot Iiico'nl'act with either, as described, whcre= by the electrode'l) is pressed into contact with the electrode 0, as and for the purpose specified.

2. The combination of the diaphragm A, to which is attached the electrode 0, the swinging electrode D, to which is attached the armature H, the magnet G, the poles of which are between the said diaphragm and armature, but not in contact'with either, and the keeper I, placed and held adjnst-ablyon said magnet byn'iagnetic attraction, as andffor the purpose specified.

3. The combination of the diaphragm A, to which is attached the'clectrode O, the swing ing electrode D, to which is attached the-armature II, and the magnet G, the poles of which 6 5 are bet ween the said diaphragm and armature,

the said armature being constructed and arranged relatively to said magnet, as described,

whereby the magnet a'c -s to draw the armas un-e downward, as well as toward the-die --7c phragm,-as and for the purpose described. v JAMES H. ROBERTSQNQ In presence ofe- A. N. VERMILYA, Gaol-M Basses. 

